The problems of shared syringes are notorious. The practice of sharing syringes without adequate sterilization between successive users is a major contributor to the transfer of Human Immunodeficiency Virus and Hepatitis with subsequent severe repercussions for the sufferer of such diseases and at a high cost to society of supporting and providing medical attention to those sufferers.
A lesser but still significant risk associated with unclean needles and syringes arises from the possibility of inadvertent needle-stick injuries. This is particularly a problem for law enforcement officers and paramedics who often encounter users of illegal drugs in their professional activities. Additionally, the habits of illegal drug users are such that dangerous byproducts of their activities, such as discarded syringes, are often left in places of public access presenting a risk to the users of areas such as public parks and school grounds.
There is clearly a need for an effective single use syringe which not only minimizes the chance of people sharing syringes, but also retracts a delivery needle into the syringe barrel, thereby inactivating the syringe and shielding the needle from inadvertent, harmful contact with other people.
Australian Patent Application No 86142198 (incorporated herein by reference in its entirety) to the present applicants discloses a single use syringe which goes a considerable way to addressing the above problem by providing a syringe barrel and plunger co-operating to rotate the plunger during use. When the plunger is rotated from its original orientation, a needle grasping mechanism is aligned with a receiving means in the needle seat. Once engaged by the grasping mechanism, the needle is retracted into the syringe barrel by retraction of the plunger.
However, the present inventors are aware that it is possible for an assiduous delinquent to re-use the above syringe by avoiding full depression of the plunger or by ensuring rotation of the plunger back into its original orientation during depression so that engagement of the plunger and needle does not occur.